Map Projections
The problem with making maps is the fact that it is difficult to show Earth’s curved surface as a flat map. Mapmakers have developed different projections to overcome this problem. In general, all projections will have some distortion, but usually there will be less distortion the smaller the area that is mapped.
Projections 1.Mercator- Shows the entire world on one continuous map. The major problem is that the higher latitudes are very distorted (stretched). Most classroom maps are Mercator projections. 2.gnomonic- Made as if a sheet of paper was put on a point on Earth’s surface. It can show the shortest route between two points, but distances and directions are distorted. 3.polyconic- These are used to show small areas, and are nearly distortion free. Because of this, they are used to make topographic maps.
Latitude and Longitude
Latitude is the distance in degrees (0º - 90º) north and south of the equator (0º). Lines of latitude are called parallels. These are imaginary lines that circle the world from east to west parallel to the equator. One degree of latitude on land is equal to 112 km (70 miles).
Longitude is the distance in degrees (0º - 180º) east and west of the prime meridian (0º). Lines of longitude are called meridians. These are imaginary lines that form half-circles and run between the North and South Poles.
Map Scale
Map scale is the distance represented on the map compared to the actual real-life distance or the ratio of distance on the map to distance on Earth. Map scales may be represented in three ways:
1. Verbally- example: “1 centimeter equals 10 kilometers”.
2. Graphically- usually a line divided into equal parts, with each part being a certain unit of length (kilometers, miles, etc.).
3. Numerically- usually shown by writing a fraction or ratio to show what part of real distances the map distances are. Example: 1/62500 or 1:62500, which means 1 unit on the map is equal to 62,500 units of real distance.
Topographic Maps
These are specialized maps which show the relief (highs and lows) of the Earth’s surface. The relief is shown with isolines (iso = same) called contour lines. These are lines that connect points of the same elevation. They also show the shape of the land. The difference in elevation between two consecutive contour lines is called the contour interval. This distance is usually noted on the map.
There are dark, thick contour lines called index contours. These are contour lines that have the elevation noted on them (these are useful when trying to determine the contour interval if it is not noted on the map). Also useful in determining elevation is a benchmark. A benchmark is a point where the actual elevation is known. The elevation is noted on a metal plate which is permanently set in the ground. The elevation is shown on the map by the letters BM and the elevation next to it (ex. BM1078). Depression contours show where the elevation decreases (a hole, volcano crater, etc.). When reading the depression contour, the elevation of the first one is the same elevation of the regular contour before it. The next one decreases the same amount as the contour interval.
Landforms on Contour Maps
The steepness of an area is show by the closeness of the contour lines. The closer the contour lines are together, the steeper the area (cliff, etc.). When the contour lines are spread out, the land is relatively flat.
A closed circle after a series of increasing contour lines shows the top of a hill or mountain.
When a contour line crosses a stream or river, the contour line bends and forms a “V” shape (see diagram). The point of the “V” shows the directionthat the water is coming from.
The slope or gradient of the hill can be determined by using a contour map (Reference Tables).
A profile (side view) of the hill/mountain can be drawn using a contour map by plotting the elevations of certain points on a vertical axis
The problem with making maps is the fact that it is difficult to show Earth’s curved surface as a flat map. Mapmakers have developed different projections to overcome this problem. In general, all projections will have some distortion, but usually there will be less distortion the smaller the area that is mapped.
Projections
1. Mercator- Shows the entire world on one continuous map. The major problem is that the higher latitudes are very distorted (stretched). Most classroom maps are Mercator projections.
2. gnomonic- Made as if a sheet of paper was put on a point on Earth’s surface. It can show the shortest route between two points, but distances and directions are distorted.
3. polyconic- These are used to show small areas, and are nearly distortion free. Because of this, they are used to make topographic maps.
Latitude and Longitude
Latitude is the distance in degrees (0º - 90º) north and south of the equator (0º). Lines of latitude are called parallels. These are imaginary lines that circle the world from east to west parallel to the equator. One degree of latitude on land is equal to 112 km (70 miles).
Longitude is the distance in degrees (0º - 180º) east and west of the prime meridian (0º). Lines of longitude are called meridians. These are imaginary lines that form half-circles and run between the North and South Poles.
Map Scale
Map scale is the distance represented on the map compared to the actual real-life distance or the ratio of distance on the map to distance on Earth. Map scales may be represented in three ways:
1. Verbally- example: “1 centimeter equals 10 kilometers”.
2. Graphically- usually a line divided into equal parts, with each part being a certain unit of length (kilometers, miles, etc.).
3. Numerically- usually shown by writing a fraction or ratio to show what part of real distances the map distances are. Example: 1/62500 or 1:62500, which means 1 unit on the map is equal to 62,500 units of real distance.
Topographic Maps
These are specialized maps which show the relief (highs and lows) of the Earth’s surface. The relief is shown with isolines (iso = same) called contour lines. These are lines that connect points of the same elevation. They also show the shape of the land. The difference in elevation between two consecutive contour lines is called the contour interval. This distance is usually noted on the map.
There are dark, thick contour lines called index contours. These are contour lines that have the elevation noted on them (these are useful when trying to determine the contour interval if it is not noted on the map). Also useful in determining elevation is a benchmark. A benchmark is a point where the actual elevation is known. The elevation is noted on a metal plate which is permanently set in the ground. The elevation is shown on the map by the letters BM and the elevation next to it (ex. BM1078). Depression contours show where the elevation decreases (a hole, volcano crater, etc.). When reading the depression contour, the elevation of the first one is the same elevation of the regular contour before it. The next one decreases the same amount as the contour interval.
Landforms on Contour Maps
The slope or gradient of the hill can be determined by using a contour map (Reference Tables).
A profile (side view) of the hill/mountain can be drawn using a contour map by plotting the elevations of certain points on a vertical axis